linux-kernel - Re: [PATCH RFC v2 2/8] drm/meson: add HDMI div40 TMDS mode

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Message-ID: <d63e5df4-2250-178e-2b1e-3a8ac8dcb6df@samsung.com>
Date:   Tue, 18 Dec 2018 13:36:53 +0100
From:   Andrzej Hajda <a.hajda@...sung.com>
To:     Neil Armstrong <narmstrong@...libre.com>, architt@...eaurora.org,
        Laurent.pinchart@...asonboard.com
Cc:     dri-devel@...ts.freedesktop.org, linux-amlogic@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC v2 2/8] drm/meson: add HDMI div40 TMDS mode

On 30.11.2018 14:42, Neil Armstrong wrote:
> Add support for TMDS Clock > 3.4GHz for HDMI2.0 display modes.
>
> Signed-off-by: Neil Armstrong <narmstrong@...libre.com>
> ---
>  drivers/gpu/drm/meson/meson_dw_hdmi.c | 24 ++++++++++++++++++++----
>  1 file changed, 20 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/meson/meson_dw_hdmi.c b/drivers/gpu/drm/meson/meson_dw_hdmi.c
> index 807111ebfdd9..b8775102b100 100644
> --- a/drivers/gpu/drm/meson/meson_dw_hdmi.c
> +++ b/drivers/gpu/drm/meson/meson_dw_hdmi.c
> @@ -365,7 +365,8 @@ static int dw_hdmi_phy_init(struct dw_hdmi *hdmi, void *data,
>  	unsigned int wr_clk =
>  		readl_relaxed(priv->io_base + _REG(VPU_HDMI_SETTING));
>  
> -	DRM_DEBUG_DRIVER("%d:\"%s\"\n", mode->base.id, mode->name);
> +	DRM_DEBUG_DRIVER("%d:\"%s\" div%d\n", mode->base.id, mode->name,
> +			 mode->clock > 340000 ? 40 : 10);
>  
>  	/* Enable clocks */
>  	regmap_update_bits(priv->hhi, HHI_HDMI_CLK_CNTL, 0xffff, 0x100);
> @@ -385,9 +386,17 @@ static int dw_hdmi_phy_init(struct dw_hdmi *hdmi, void *data,
>  	/* Enable normal output to PHY */
>  	dw_hdmi_top_write(dw_hdmi, HDMITX_TOP_BIST_CNTL, BIT(12));
>  
> -	/* TMDS pattern setup (TOFIX pattern for 4k2k scrambling) */
> -	dw_hdmi_top_write(dw_hdmi, HDMITX_TOP_TMDS_CLK_PTTN_01, 0x001f001f);
> -	dw_hdmi_top_write(dw_hdmi, HDMITX_TOP_TMDS_CLK_PTTN_23, 0x001f001f);
> +	/* TMDS pattern setup (TOFIX Handle the YUV420 case) */
> +	if (mode->clock > 340000) {
> +		dw_hdmi_top_write(dw_hdmi, HDMITX_TOP_TMDS_CLK_PTTN_01, 0);
> +		dw_hdmi_top_write(dw_hdmi, HDMITX_TOP_TMDS_CLK_PTTN_23,
> +				  0x03ff03ff);
> +	} else {
> +		dw_hdmi_top_write(dw_hdmi, HDMITX_TOP_TMDS_CLK_PTTN_01,
> +				  0x001f001f);
> +		dw_hdmi_top_write(dw_hdmi, HDMITX_TOP_TMDS_CLK_PTTN_23,
> +				  0x001f001f);
> +	}
>  
>  	/* Load TMDS pattern */
>  	dw_hdmi_top_write(dw_hdmi, HDMITX_TOP_TMDS_CLK_PTTN_CNTL, 0x1);
> @@ -413,6 +422,8 @@ static int dw_hdmi_phy_init(struct dw_hdmi *hdmi, void *data,
>  	/* Disable clock, fifo, fifo_wr */
>  	regmap_update_bits(priv->hhi, HHI_HDMI_PHY_CNTL1, 0xf, 0);
>  
> +	dw_hdmi_set_high_tmds_clock_ratio(hdmi);
> +
>  	msleep(100);
>  
>  	/* Reset PHY 3 times in a row */
> @@ -562,6 +573,11 @@ dw_hdmi_mode_valid(struct drm_connector *connector,
>  		mode->vdisplay, mode->vsync_start,
>  		mode->vsync_end, mode->vtotal, mode->type, mode->flags);
>  
> +	/* If sink max TMDS clock < 340MHz, we reject the HDMI2.0 modes */
> +	if (mode->clock > 340000 &&
> +	    connector->display_info.max_tmds_clock < 340000)
> +		return MODE_BAD;
> +


Why not just:

if (mode->clock > connector->display_info.max_tmds_clock)
	return MODE_BAD;


Regards

Andrzej


>  	/* Check against non-VIC supported modes */
>  	if (!vic) {
>  		status = meson_venc_hdmi_supported_mode(mode);